Kara was summoned to Cadmus when Lillian Luther kidnapped Mon-El. When she arrived, she met who she thought what J'onn — but turned out to be the original Hank Henshaw. As it turns out, not only is Hank just as xenophobic against alien life, but he has been enhanced by Cadmus. That's not a great combination. He and Kara fought, and then Kara was subject to a bunch of Cadmus experiments before she and Mon-El managed to escape. They took a vile of her blood, and everything.

In the comics, Henshaw was an astronaut and Cyborg Superman was "created" after an accident in space gone wrong. He blames Superman for what happened to him and becomes a villain. It's a slightly different origin story than what we're getting on the CW series, but just as menacing.

At the end of the episode, Cyborg Superman went to the Fortress of Solitude and used Kara's blood to hack into the computer system. He asked about "Project Medusa." So that's mysterious and shady. Not only that, but Jeremiah is some kind of cool underground hero within the walls of Cadmus? Amazing. Also, J'onn is turning into a White Martian, the DC vigilante Barrage appeared, and everyone's newest 'ships are taking baby steps forward. There's a lot being set up right now on Supergirl. The upcoming "Heroes versus Aliens" event on the CW will be a much needed departure.